The application relates to a method, which is particularly suitable for the separation of fluorinated organic compounds from fluids, a kit that is used therefore, and an especially soluble first adsorbent component with a lipophilic group and a hydrophilic group that can be used therefore. In this connection, on the one hand, the contaminated fluid comes into contact with at least the first, as a rule amphiphilic, adsorbent component. There can then be a contact with a second solid adsorbent component, which makes possible a adduct formation, so that the loaded adsorbent material can be separated from the purified fluid. Fluorinated organic compounds have excellent and unique technological properties, which is why they have long been utilized in many different industrial products and processes (for example, as textile and paper finishes, as water and dirt repellent coatings, as hydraulic fluids, as fire extinguishing foams, in the production of Teflon as well as in electroplating). Owing to their specific properties, there are frequently no alternatives to these substances.
Fluorinated compounds, in particular perfluorinated surfactants, are, however, potentially toxic to the environment as well as to humans, which is a result of the high tendency to bioaccumulation. Perfluorinated surfactants have in recent years been ubiquitously found in the environment because of their high persistence. They are basically released to the environment via wastewater from the production processes of fluorochemical products, or as a result of the use and release of the corresponding products to the environment. By way of example, perfluorinated surfactants, such as foaming agents in fire extinguishing foams as well as humectants and antifogging agents in the electroplating, photography or semiconductor industries, should be mentioned.
The provisions and guidelines and regulations of many countries, for example, the European Directive 2006/122/EG have drawn attention to the dangers of perfluorinated octanoic acid and perfluorinated sulfonic acids and their use has been greatly restricted.
Perfluorinated surfactants are, however, indispensable in a series of industrial processes, in particular in electroplating, in fire protection as well as in photography and in semiconductor technology; exceptions for those applications have therefore been incorporated in the latest legal regulations. These substances are used, for example, in occupational safety in electroplating technology (antifogging agents and humectants); they are used as a foam barrier or liquid fume suppressant for the immobilization of the very harmful and carcinogenic chromic acid.
Different provisions have currently been implemented in plants in order to reduce the discharge of fluorinated organic compounds, in particular highly toxic compounds, such as special perfluorinated surfactants (PFS), into wastewater and ground water. The separation and separate disposal of the wastewater substreams loaded with these components should be particularly mentioned. The use of various treatment methods for wastewater and ground water purification is of particular importance for this purpose.
During purification, however, the problem is that, due to their chemical and physical properties, perfluorinated surfactants can, in particular, not be effectively separated from contaminated fluids, either with conventional biological methods or by means of classical physical methods, such as stripping.
US 2007/01381-10 describes, for example, the separation of perfluorinated surfactants by means of capacitive deionization of contaminated water. This method is, however, too cost intensive with regard to procurement, operation and maintenance of the plants for the purification of large amounts of wastewater. This likewise applies to wet oxidative methods, for example, by means of UV, ozone, peroxide or microwave irradiation. In some physical separation methods, such as membrane technology, highly concentrated aqueous solutions are left as waste, whose (thermal) disposal is difficult and thus uneconomic.
The chemical separation methods in particular include adsorption methods. Adsorbent resins, for example, are used for the purification of wastewater. They have a very selective adsorption capability and a great absorptive capacity with respect to high pollutant concentrations. WO 2008/066748 A1 discloses, for example, the use of ion exchangers. Nevertheless, the adsorbent resins could not gain acceptance as adsorptive materials for the conditioning of wastewater and ground water. They are comparatively more expensive than activated carbon and their regeneration is more complex.
Adsorption on activated carbon is therefore frequently used for the purification of wastewater containing PFS. Fluorinated surfactants, in particular short-chain perfluorinated surfactants, can, however, not be selectively separated herewith.
EP 1 561 729 A1, for example, discloses an adsorption method based on activated carbon for separating fluorinated emulsifiers in wastewater containing particles of fluoropolymers. Non-ionic or anionic surfactants are added to the wastewater for this purpose in order to prevent the deposition of polymer particles on the activated carbon and a consequent clogging of the filter.